1. Field of the Invention
This invention relates to an electrochemical sensor for determining the oxygen content in gases, particularly in exhaust gases of burners or internal-combustion engines, having an ion-conducting solid-electrolyte tube closed on one side, supported by a housing, and electrodes on the inner and outer surfaces of the tube,
2. Description of the Prior Art
In one known sensor of this type, the contact areas are formed in part by the electrodes placed on the inside and outside of the solid-electrolyte tube. The potential leads provided for taking off the voltage each have a resilient, electrically conducting mass which is pressed by means of a spring element into the gap between the outer electrode and the housing as well as into the gap between the inner electrode and a tubular connector part which leads to the outside and is insulated against the housing (German Published Non-Prosecuted Application No. 2 350 253). In addition to the expensive design, particularly because of the potential lead mechanism, the main disadvantage of the known sensor is that the outer electrode is connected to the metallic housing and therefore, to ground. At the ground connection, which is effected via a screw thread at the housing, oxide layers and thus, contact resistances and/or thermoelectric interference voltages readily occur at the high operating temperature of the sensor. Such changes can reduce or falsify the measurement signal. This danger is the greater, as the screw thread is arranged in the immediate vicinity of the sensor tip and therefore, in the proximity of high temperatures.